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' UNITED STATES PATENT FFIGE.

SAMUEL HUFTY, OF CAMDEN, NEW JERSEY, AND JOSEPH K. CALDWELL, OFPHILADELPHIA, PENNSYLVANIA.

PROCESS OF CONVERTING CAST-IRON INTO STEEL.

SPECIFICATION forming part of Letters Patent No. 536,083, dated March19, 1895.

Application filed une 2, 1893. Renewed November 8, 1894- Serial No.528,261. (No specimens.)

To aZZ whom it may concern.-

Be it known that we, SAMUEL I-IUFTY, of Camden,New Jersey, and JOSEPH K.CALD- WELL, of Philadelphia, Pennsylvania, both citizens of the UnitedStates, have invented certain Improvements in Converting Cast- Iron intoSteel, of which, the following is a specification.

The object of our invention is to remove a certain portion of the carbonfrom cast iron or iron containing carbon in such proportion that itishard and brittle, whereby We are enabled to convert such iron into steelofsuch ductility that it can be shaped, hammered, drawn, or rolled inthe same manner as steel produced in the ordinary way or can be temperedin order to form cutting tools or for other purposes for whichtemperingis usually resorted to.

The mainfeature of our invention consists in subjectingthe cast ironWhile highlyheated, but still considerably below the point of fusion, tothe action of the gases resulting from the decomposition by heat ofnitro-muriatic acid. This acid (the aqua-regia of commerce) is a verypowerful oxidizingagent, differingin its action from either nitric acidor muriatic acid, and we have found that the gases resulting from itsdecomposition under heat, have the efiect of attacking and removingcarbon in the form in which the same is found in cast- Thenitro-muriatic acid can be decomposed directly in the furnace orcrucible containing the metal, or the gases resulting from thedecomposition of the acid can be introduced into such furnace orcrucible, if the decomposition is efiected in a separate vessel. 7 i

In carrying out our invention the quantity of acid to be used and thetime during which the treatment is continued will, of course, vary,depending upon the bulk of the iron under treatment and the extent ofconversion required, increased bulk of material requiring an increasedquantity of acid and the extent of conversion being greater or less,depending upon the length of time duringwhich the iron is subjected tothe action of the gases. As an instance, however, of what maybe done inthe practical carrying out of our invention we may say that in thetreatment of ordinary. white iron the use of thirty ounces of the acidto every one hundred pounds of the iron will give good results. i

We are aware that it is old to treat molten iron with a mixture ofhydrochloric and muriatic acids, but such treatment could not accomplishthe result obtained by us since a failure to secure the proper grade orsoftness of steel in castings made from the mass of molten iron can notbe remedied; whereas, by treating the cast iron in, solid forms withnitro-muriatic acid, we are enabled to retreat the same castings at anytime when the proper or desired softness is not obtained in the firsttreatment; and furthermore, our castings are not subjected to the actionof subsequent fusion.

Having thus described our invention, we claim and desire to secure byLetters Patent The herein described process of decarbonizing cast iron,consisting in subjecting the solid metal to the action of high heat andthe gases resulting from the decomposition of nitro-muriatic acid,substantially as described. In testimony whereof we have signed ournames to this specification in the presence of two subscribingwitnesses.

SAMUEL HUFTY. JOSEPH K. CALDWELL.

WVitnesses:

FRANK E. BECHTOLD, JOSEPH H. KLEIN.

